Polypropylene resins have excellent mechanical strength, rigidity, heat resistance, chemical resistance, oil resistance, transparency, low temperature impact strength and the like. Utilizing these characteristics, they are widely used as packaging and covering materials such as film, sheet and bottle, or ornament materials such as wallpaper. However, since such polypropylene resins have high permeability of gas such as oxygen, they were not used as a packaging material for food, medicine, cosmetics and the like, where high gas barrier property is required. Therefore, in order to improve the gas barrier property of a polypropylene resin, a method of laminating the polypropylene resin with a resin having better gas barrier property than the polypropylene resin such as a saponified ethylene.vinyl acetate copolymer has been proposed. In this case, however, as adhesiveness of polypropylene with the saponified olefin.vinyl acetate copolymer (hereinafter called EVOH) is very poor, various adhesive resins such as ionomer, ethylene.vinyl acetate copolymer, and graft-modified carboxylic acid are co-extruded to obtain a laminate structure (Patent Document 1).
However, when such a laminate structure is filled with a content at high temperature, or heat treated thereafter, delamination of EVOH and the adhesive resin takes place in such occasions as secondary processing, dropping or bending due to expansion and shrinkage. Furthermore, whitening due to bending may occur, leading to unsatisfactory performance (such as strength) or appearance of the product. Moreover, the EVOH layer tends to develop cracks due to delamination of EVOH and the adhesive resin layer, which may cause deterioration of barrier property.
In the case of ornament materials such as wallpaper, peeling of the adhesive resin layer from a base material (resin film, metal) may occur under an environment of repeated heating and cooling, which may spoil the appearance.    [Patent Document 1] Japanese Patent Laid-open Publication No. 2001-88249